As far as story line goes there isn't much, partly because of the series only lasting 5 episodes but also that it wasn't developed that much either. The plot line of why things are the way they are in this twisted universe is not explained, we're given a VERY brief reason to why and it doesn't make much sense aside from 'everyone wants to kill everyone'. Sadly to say the story can be summed up in one line and that is "All warriors want to be Number One". With all its flaws and open holes in the story, it still remains interesting because there has been nothing else quite like it. Seriously, when is the next time you'll see a animation about a Black Samurai with a rippin' Afro kicking some serious butt? Probably not for a looooong time.
The art style can well referenced to being very similar -if not the same as- to the art used in Todd McFarlane's "Spawn" the TV series. It can be described as a very flowing but detailed art style with often a dark tone to it. The attention put into the finer details in the art form to make the action really come to life and defining the scene, it gives a surreal feel to the series. I particularly like this art style for its detail alone but the dark overtones really sets off really dark series like this one very well.
The characters in this series are movie motion perfect for an action series and fit greatly into their roles but something is lacking. We learn very little to nothing about the characters in the series and what we are given we have to use our own imagination to fill in, which isn't too bad I guess (again, if it was more than 5 episodes I'm sure there would have been more). Artistically the characters are well formed but they lack strong vocal characterization. What I mean to say is that most of the characters and dialogs sound as if a poor designed robot is try to articulate emotions it knows nothing about. More work could have been put in.
Overall? This is a series that should be watched just for being what it is, a super-awesome-bad-ass-black-samurai-adventure. Not the greatest animation out there but like I said before, when else are you going to run into something this different.
